Conversion of hydrocarbons



Aug. 17, 1943. DU Bols EAsTMAN 2,327,099

CONVERSION 0F HYDROCARBONS l Filed Nov..9. 1940 CONDENSER cATALYs-r cAsE TH ERMAL REACTION ZONE Du Bols EASTMAN IN VEN TOR H/S fl TORNE Patented Aug. 17, 1943 UNITED STATES `PATENT OFFICE 2,327,099 CONVERSION or nYnooAaaoNs Du Bois Eastman, Port Arthur, Tex., assignor, by mesne assignments, to The Texas Company, New York, N. Y., a corporation oi' Delaware Application November 9, 1940, Serial No. 365,056

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This invention relates to a combination catalytic cracking and thermal cracking process for the conversibn of hydrocarbons to convert the surface, such as catalysts of the silica-alumina type, capable of catalyzing the conversion reac- .tions and in which the products of conversion are separated from the catalyst and subjected to thermal conversion in contact with-heatedcycle condensate formed in the process to effect additional conversion into gasoline hydrocarbons.

When hydrocarbon oil is subjected to catalytic cracking it is found that the insumciently converted products, that is, particularly, the constituents of the kerosene and gas oil boiling ranges, are not as well suited for further catalytic cracking as the raw charging stock and it is more advantageous to subject such insuiiiciently converted constituents to thermal cracking than to either recycle them to the catalytic conversion zone or crack them in a separate catalytic cracking zone. In accordance with the invention these insufliciently converted constituents are passed through a heating zone and combined with `the cracked products from the catalytic cracking* zone so as to eil'ect further conversion.

In the process the raw charging stock such as straight run gas oil, is passed through a heating zone wherein it is heated to a desired conversion temperature and directed into a catalytic cracking chamber containing a bed of catalytic material, the resultant products of conversion are withdrawn from the catalyst bed and directed into a subsequent thermal conversion chamber wherein the products of the catalytic cracking are subjected to thermal conversion in contact with heated cycle condensate, the resultant proding range and is then combined with the catalytically cracked products and the admixed products subjected to further thermal conversion.

'I'he invention makes it possible to operate at a relatively low cracking per pass and high charging rate in the catalytic cracking zone so as to thereby greatly increase the life of the catalyst and yet obtain a high ultimate yield of anti-knock gasoline as a result of the additional conversion in the subsequent thermal conversion zone.

For the purpose of more fully explaining'the invention reference is now had to the accompanying drawing which shows one form of apparatus adapted for practicing the invention.

In the apparatus illustrated the catalytic cracking stage of the process is practiced by .heating the raw oil or charging stock in a heating coil I0, suitably disposed in a furnace I I, to the desired conversion temperature and passing the heated oil to a catalyst case -I2 containing a bed of catalytic material. In practice, a plurality of catalyst cases are employed so as to provide for the reactivation of the catalyst without disturbing the continuity of the process. The products of the catalytic cracking operation are conducted through a line I3 to a thermal reaction chamber Il which is suitably insulated against heat loss. The reaction chamber illustrated is of the low liquid level type being provided with a residue draw-off line I5 and a vapor line I6 extending from a lower section of the reaction chamber to a fractionating tower I'i. The tower I1 is equipped with suitable fractionating elements such as bubble trays or the like and with the necessary cooling and retluxing means to accomplishl the desired fractionation. The reflux condensate comprising constituents higher boiling than gasoline is withdrawn from tower I'Iv through a line I8 and is conducted by pump- I9 and line 20 to a heating coil 2i suitably disposed in a furnace 22 for subjecting the condensate to a cracking temperature, andthe heated products from coil 2i are passed through a transfer line 23' to the reaction chamber I4 or to the transfer line I3 so that the heated cycle condensate may be combined with the conversion products from the catalytic cracking chamber I2 and the admixed products subjected to thermal conversion in reaction chamber I4. 'I'he overhead vapors from the tower l 'I pass to` a condenser 24 and the gasoline or motor fuel distillate is collected in a receiving drum or gas separator 25, the liquid distillate being withdrawn through a line 26. Uncondensed components consisting essentially of normally gaseous hydrocarbons pass through a line 21 to an absorber 28. The charging oil for the'process is charged by a pump 2'9 through a line 30 having a branch line 3| extending to the absorption tower 28 and another branch line 32 communicating with a line 33 which extends to the heating coil I Il, so that the charging oil` may either be passed directly to the heating coil I0 or into the absorption tower 28, or a portion may be passed directly to the heating coil and the other portion introduced into the absorption tower. The charging oil introduced into the absorption tower absorbs normally gaseous constituents particularly C3 and C4 hydrocarbons and the enriched oil is drawn from the bottom of the tower and directed by a pump 34 through line 35 thence to line 33. The unabsorbed gases leave the tower through a gas line 36.

In practicing the invention the use of the synthetic silica-alumina type of catalysts is recommended. Various acid-treated and metalsubstituted clays such as the Super-Filtrols and acid-treated and metal-substituted natural or artificial zeolites, such as the artificial zeolite known as Doucil may be employed. Various metals such as uranium, molybdenum, manganese, lead, zinc, zirconium, nickel and the like, may be substituted in the clays or zeolites. Likewise, the combination of certain acid-treated active clays of the character of Filtrol, together with added proportions of alumina or silica or both may be employed. Alumina alone may be used under certain conditions. The synthetic alumina catalysts can be improved by the addition of other constituents such as zirconium oxide or molybdenum oxide. invention the charging stock, such as straightrun gas oil and preferably a stock capable of being substantially completely vaporized, is heated sufficiently to maintain cracking temperatures of `the order of 850 F.-1050 F. and preferably temperatures of 910 F.-1000 F. in the catalyst case. The oil is preferably heated in the heating coil so that it will be delivered to the catalyst case in a substantially completely vaporized condition and it is desirable to avoid deposition of liquid oil orfcondensationv on the catalyst. In the catalytic operation pressures within a range from atmospheric pressure up to approximately 200 lbs. are ordinarily most efiicient but in the practice of the invention it is desirable to maintain pressures approximating the upper limit of this range so as to facilitate the maintenance of reasonably high superatmospheric pressures in the subsequent thermal conversion zone. In the recycling cracking zone the oil is subjected to temperatures upwards oi 850 F. and preferably temperatures of about 900 F. to 950 F. under superatmospheric pressure of about 200 lbs. up to 600 or 800 lbs. The mixture of catalytically cracked products and products from the recycling cracking coil is maintained under temperatures of about 850 F.-925 F. under pressures approximating the pressure in the catalytic cracking zone.

In a typical` example of the invention a straight-run gas oil of 650 F. end point is heated in the heating coil I and delivered to the catalyst case at a temperature of 980'F. wherein a pressure of 210 lbs. is maintained. The cycle condensate is subjected to cracking in the heating coil with an outlet temperature of 950 F.

In practicing theV under 250 lbs. pressure and the admixed products from the catalytic cracking zone and from the recycling cracking coll are maintained in the thermal soaking zone at a temperature of 900 F. under 200 lbs. pressure.

In the practice of the invention the catalytic cracking of the liquid oil charge is conducted in a once-through or single-pass manner although when the charging stock contains norA mally gaseous constituents absorbed from the eilluent gases the operation in the catalytic cracking zone will be cyclic as regards the normally gaseous constituents. y

While I haveffxdescribed a particular embodiment of my invention for purposes of illustration. it should be understood that various modincations and adaptations thereof which will be obvious to one skilled in the art, may be made within the spirit of the invention as set forth in the appended claims.

I claim:

1. In the manufacture of high antiknock gasoline, the process that comprises passing straightrun gas oil charging stock through a single-pass catalytic cracking zone wherein the oil is subjected to cracking ktemperature in Vthe presence of a catalyst adapted to promote conversion into lower boiling hydrocarbons of the gasoline boiling range, removing the resultant cracked products from said catalytic cracking zone and directing said products to a subsequent thermal cracking zone, heating cycle condensate to a cracking temperature in a heating zone and delivering the heated condensate into said subsequent thermal cracking zone wherein the admixed products are maintained at a cracking temperature of the order of 850 F.925 F. and subjected to conversion, separating the resultant products of conversion into vapors and resid/ue, fractionating the separated vapors to separate a reflux condensate from lighter products. and directing said reflux condensate to said heating zone as said cycle condensate.

2. In the manufacture of high antiknock gasoline, the process that comprises passing straightrun gas oil charging stock through a single-pass catalytic cracking zone wherein the oil is subjected to cracking temperature in the presence of a catalyst adapted to promote conversion into lower boiling hydrocarbons of the gasoline boiling range, removing the resultant cracked products from said catalytic cracking zone and directing said products to a separating and cracking zone wherein separation of vapors from residue takes place at cracking temperature, heating cycle condensate to a cracking temperature in a heating zone and delivering the heated condensate into said separating and cracking zone wherein the admixed products are maintained at a cracking temperature of the order of 850 F.925F. and subjected to conversion, conducty. ing the separated vapors to a fractionating zone wherein the vapors are subjected to fractionation to separate a reflux condensate from lighter products, and directing said reux condensate.

to said heating zone as said cycle condensate.

3. In the manufacture of high antiknock gasoline, the process that comprises p raw charging stock in single pass through a heating coil in which the oil is vaporized and heated to a cracking temperature, directing the heated vapors in single pass through a catalyst chamber wherein the oil is subjected to cracking temperature in the presence of a catalyst adapted to promote conversion into lower boiling hydrocarbons of the gasoline boiling range, removing the resultant cracked products from said catalysty chamber and directing'said products to a subsequent thermal cracking zone, heating cycle condensate to a cracking temperature in a heating zone and delivering the heated condensate into said subsequent thermal cracking zone wherein the admixed products are mainy ,tained at a cracking temperature of the order of. v850 F.925 F. and subjected to conversion. separating the resultant products of' conversion into vapors and residue, fractionating the sepaV rated vapors' to separate a reux condensate from lighter products, and directing said'reux condensate to said heating zone as said cycle condensate.

' DU BOIS EAS'IMAN. 

